Well my trio were hatched January 28th. I got to weigh them the other night and they were right around 5lbs. I'm hoping they continue to plump up. They do free range daily though. I won't be butchering any of these, so will have to wait for babies next year to find out a true measure.
A chicken problem would show up as non-fertile eggs in the first place, or a lot of blood rings a week into incubation. I'd start thinking it was the breeders at that point (if the thermometer has been accurate). If you get chicks to the hatcher and they don't make it out of the shells, then it's more likely a humidity problem (too high all during incubation).
I didn’t end up keeping them. I’m running low on room hahaha. I’m trying to decide who to keep from my layer flock so I can make room for some Delaware’s. My daughter got some bantams that are taking up my little coop :-/